Airfield lighting unit



May 26, 1964 E. s. CALVERT ETAL 3,134,959

AIRFIELD LIGHTING UNIT Filed Aug. 2, 1960 5 Sheets-Sheet 1 EDWARD SPENCECALVERT JACK WALTON SPARKE ROWLAND HENDRY REDMIL BERTRAM STEVENS PETERJOHN COOPER INVENTORS ATTORNEY y 1964 E. s. CALVERT ETAL 3,134,959

AIRFIELD LIGHTING UNIT Filed Aug. 2, 1960 5 Sheets-Sheet 2 y 26, 1954 E.s. CALVERT ETAL 3,134,959

AIRFIELD LIGHTING UNIT 5. Sheets-Sheet 3 Filed Aug. 2, 1960 y 26, 1964E. s. CALVERT ETAL 3,134,959

AIRFIELD LIGHTING UNIT Filed Aug. 2, 1960 5 Sheets-Sheet 4 y 26, 1964 E.s. CALVERT ETAL 3,134,959

AIRFIELD LIGHTING UNIT 5 Sheets-Sheet 5 Filed Aug. 2. 1960 Patented May26, 1964 3,134,959 AIRFIELD LIGHTING UNIT Edward S. Calvert, Jack W.Sparke, and Rowland H. Redmiil, Farnborough, and Bertram Stevens andPeter John Cooper, London, England, assignors to Thorn ElectricalIndustries Limited, London, England, a British company Filed Aug. 2,1960, Ser. No. 46,930 Claims priority, application Great Britain Aug.31, 1959 7 Claims. (Cl. 340-26) The present invention relates tolighting units of the type which are employed at airfield runways (or onflight-decks) to provide the pilot of a landing aircraft with visualinformation regarding a path to be followed in making a safe landing.

A system in which such lighting units are employed is described in thespecification of British specification 830,043, published March 9, 1960,and also in an article on The Theory of Visual Judgment and ItsApplication to the Deisgn of Landing Aids for Aircraft, by ES. Calvert,Trans. Ill. Eng. 22, 1957, page 278.

The system as described in the above-mentioned specification uses twopieces of apparatus for producing two beams of light each dividedhorizontally substantially about a medial plane into two contrastingportions, the two medial or division planes of said beams, respectivelyenclosing a small dihedral angle or being substantially parallel, and sopresenting to the view of the approaching pilot one of three visualindications dependent on whether he is inside the angle between saidplanes or outside said angle in the upward or downward direction.

The specification describes a system for indicating an inclined glideslope plane is which system each apparatus consists of a light sourceand a reflector in front of the upper half of which is disposed ared-passing filter having a straight lower edge which extendshorizontally and as opaque screen formed with a narrow straight-edgedhorizontal slot or opening parallel to the straight lower edge of thefilter and through which the axis of the reflector extends at rightangles. The light source and reflector are such that the beam therefromis focused upon the slot in the opaque screen from which the lightissues in a divergent beam divided at a medial plane defined by thelower edge of the filter and the median line of the slot into an upperwhite portion and a lower red portion.

In the practical use of such apparatus they are installed close to therunway of airfields in such a position that servicing is not easy at alltimes. It is essential that such units should be in full operatingcondition as far as possible all the time and also that the adjustmentof the units should be to the required accuracy. In all suggested unitsconsiderable skill was needed is adjustment particularly when servicinginvolved change of the light source.

It is also desirbale for the equipment to be light and frangible so asto present the minimum of obstruction in the event of an aircraftcolliding with the apparatus.

It is the object of this invention to provide a lighting unit that willrequire minimum adjustment on site on first installation. It is afurther object of the invention to provide a unit in which lamp changesmay be made very quickly and without any adjustment being required onthe site.

According to the invention in one aspect a lighting unit of the typespecified comprises a substantially flat base member adapted to beanchored to and be held rigid by a fixed structural support and aself-contained rigid optical bench comprising a lamp or lamps, a screenwith a horizontal slot and, between the lamp or lamps and the screen, orbetween each lamp and the screen, a filter member divided horizontallyinto portions imparting two different colors to light transmittedtherethrough, whereby in operation a beam of light divided horizontallysubstantially about a medial plane into two contrasting portions isproduced, wherein the lamp or each lamp is fixed to a mounting member inpreset locations and orientation and wherein the mounting member isreleasably held in the optical bench in invariant location andorientation with respect to the bench.

According to the invention in yet another aspect a lighting unit of thetype specified comprises a substantially flat base member adapted to beanchored to and held rigid by a fixed structural support and aself-contained rigid optical bench comprising a lamp or lamps, a screenwith a horizontal slot and, between the lamp or lamps and the screen, orbetween each lamp and the screen, a filter member divided horizontallyinto portions imparting two different colors to light transmittedtherethrough, whereby in operation a beam of light divided horizontallysubstantially about a medial plane into two contrasting portions isproduced, the optical bench being mounted on the base member by means ofadjusting members which enable the orientation of the optical benchrelative to the base member to be adjusted and the lamp or each lamp isfixed to a mounting member in preset location and orientation andwherein the mounting member is releasably held in the optical bench ininvariant location and orientation with respect to the bench.

The lamp or each lamp may either comprise a separate bulb and reflector,in which case pre-adjustment of the bulb with respect to the reflectoris necessary, or a sealed beam unit in which the reflector isconstituted by part of the wall of the bulb.

By utilising an optical bench adjustable with respect to a base memberand arranging the bench to be a selfcontained rigid entity in whichlamps are mounted in an orientation determined by factory adjustmentand, no service adjustment of such features is required; serviceadjustment is restricted to adjustment of the orientation of the opticalbench with respect to the base member. The adjusting members by means ofwhich the optical bench is mounted on the base member preferably consistof three screw fixings, adjustment of any of which affects the spacingbetween the base member and the optical bench at the point of thefixing. The fixings are preferably arranged in a triangle having oneside transverse of the lighting unit.

The base member does not have to be of heavy construction since itacquires its rigidity from the structural support to which it is boltedor otherwise anchored. The whole unit can be provided with alight-weight protective cover suitably slotted to allow emergence of therequired beam of light. The whole unit can be of low weight and offrangible construction such as to present very little obstruction to anaircraft striking it.

The invention will now be described in greater detail by way of furtherexample with reference to the accompanying drawings. In the drawings,which are not to scale:

FIG. 1 is a perspective view of the base member of a unit embodying theinvention,

FIG. 2 is a perspective view of the optical bench of the unit,

FIG. 3 shows the details of one of three mounting bolts used to fix theoptical bench to the base member,

FIG. 4 shows a detail of the optical bench,

FIG. 5 is a perspective view of the complete unit, including a cover,

FIG. 6 is a diagrammatic cross-section of the complete unit,

FIG. 7 is a front view of an alternative construction 7 of a lamp forthe unit, and

.3 consists of a flat, rectangular frame of light alloy angle members10, stiffened by four corner plates 11. Each plate 11 has bolted theretoa pedestal 12 having an apertured flange 13 which can be bolted on to aconcrete block or other fixed structural support.

Three threaded studs 14, 15 and 16 are bolted to the base member at thecorners of an isosceles triangle and have conical depressions 17 intheir upper ends.

Turning now to FIG. 2 the optical bench of the unit is built up of lightalloy angle and tubes and supports in three spaced, substantiallyparallel, vertical planes, a horizontally slotted plate 20, a filterscreen 19 and three lamps 18. The filter screen 19 is dividedhorizontally into a lower clear half and an upper red half and as may beseen in FIG. 4 is fluted vertically in order to give the beam of lightthe desired lateral spread. This figure also shows how the filter screen19 is held in a frame 21 which is slidable vertically in channel members22 either side of the optical bench of the unit. Screws 23 enable thescreen to be locked at any desired vertical setting. The slotted plateis similarly adjustable. These adjustments are intended to be madesolely in the factory and enable the lamps 18, the divison in the filterscreen 19 and the slot in the plate 20 to be lined up with the saiddivision and slot truly parallel. It may even be desirable to so lockthe filter screen 19 and the plate 20 after the factory adjustment hasbeen made that the service mechanic is not able to tamper with theadjustment.

As is best seen in FIG. 6 the lamps 18, each with a source 24 and areflector 25, screen 19 and plate 20, between them enable a horizontallydivided beam of light to be set up, the lower half of the beam emergingfrom the slot in the plate 20 being red and the upper half being white.

The optical bench (FIG. 2) has three plates 26 in its base plane andbolts 27, 2-8 and 29 are mounted vertically in the plates respectively.When the optical bench is placed on the base member the ends (which arerounded) of the bolts 27, 28 and 29 stand in the depressions 17 of thestuds 14, 15 and 16 respectively. The studs 14 and 15 and the bolts 27and 28 lie on a line transverse of the unit and the stud 16 and bolt 29are on the centre line of the unit. Adjustment of the bolts 27 and 28tilts both the filter screen 19 and the plate 20 together and hence thedivision of the beam 30 for transverse horizontally whilst the bolt 29enables adjustment of the angle of elevation of the median plane of thebeam to be made. Clearly these adjustments are made solely by adjustmentof the orientation of the optical bench with respect to the base member.No adjustments within the optical bench are required.

The details of construction associated with the bolt 29 and stud 16 areshown in FIG. 3. The bolts 29 screws through a collar 31 welded to theplate 26 and a nut 32 enables the bolt to be locked against furthermovement once adjustment has been effected. The stud 16 is fixed to aplate 33 of the base member by a nut 34.

A circlip 35 fits in a groove towards the lower end of the bolt 29 andretains an internally flanged nut 36. The nut 36 is screwed on to thestud 16 and by engagement with the circlip 35 holds the bolt 29 firmlyin place.

As can be seen in FIG. 2 each lamp 18 is mounted on a back-plate 37which slots into vertical channels 38 being retained by clips 39 whichembrace one of the tubes 40 of the framework. Changing a burnt-out lampis a simple operation and by arranging at the factory that the lamps 18have an invariant orientation with respect to the plates 38, changing alamp does not involve any readjustments being made. To this end theplates 38 must of course seat in their retaining fixture without playand are not adjustable with respect to the framework.

FIGS. 7 and 8 illustrate a lamp in greater detail and also show analternative and more positive way of fixing the plates 38 in the opticalbench. Each plate 38 is apertured to receive its lamp and also hasriveted or spotwelded to it a back cover 41 and a front cover orcondensate drip shield 42. A plug 43 is mounted in the back cover 41 andone lead 44 to a bulb terminal 45 can be seen. The embodiment of lampshown in a sealed beam unit in which the reflector 25 is constituted bypart of the bulb wall.

The reflector 25 has three seatings 46 formed therein at intervals andthese rest on three adjusting screws 47 passing through the plate 38.The reflector is clamped against the screws 47, which allow factoryadjustment over a small range of angles to be made, by means of a ring48 fixed to the plate 38 by spring loaded nut and bolt fixings 49.

The plate 38 has four threaded apertures in predetermined locations inits four corners respectively. In the optical bench these are engaged bycaptive screws 50 in brackets 51 fixed to tubes 52 of the framework. Thebrackets, which provide seating surfaces for the plate, and screws andcorresponding apertures in the plate 38 constitute a fixing giving theplate 38 an invariant position and orientation with respect to theframework of the unit.

Instead of using one elongated rectangular filter screen for all threelamps it may be preferred to provide each lamp with an individual roundfilter screen mounted in a plate fitted in the optical bench in the sameway as the lamp shown in FIGS. 7 and 8. Each screen would accordinglyappear much as the lamp as shown in FIG. 7 except that the division intoan upper red half and a lower clear half would be apparent. Thisarrangement has a number of advantages. The risk of fracture of thescreen on account of uneven heating is less than is the case with arectangular screen. However should a screen fracture it can be replacedby the service mechanic without any adjustment being required.

As shown in FIG. 5 the complete unit is provided with a three-piececover 53, 54, 55, the front piece 55 having an aperture 56 around theslot in the plate 20. In the arrangement shown, padlocks 57 and bars 58prevent unauthorised removal of the cover.

We claim:

1. A lighting unit for use at an airfield runway or the like to providea pilot of a landing aircraft with visual information regarding a pathto be followed in making a safe landing, comprising a substantially flatbase member adapted to be anchored to, and be held rigid by a fixedstructural support and a self-contained rigid optical bench comprisingat least one lamp, a screen with a horizontal slot and, between the lampand the screen, a filter member divided horizontally into portionsimparting two different colors to light transmitted therethrough,whereby in operation a beam of light divided horizontally substantiallyabout a median plane into two contrasting portions is produced, andadjusting members by means of which the optical bench is mounted on thebase member, the adjusting members enabling the orientation of theoptical bench relative to the base member to be adjusted.

2. A lighting unit according to claim 1, wherein the said adjustingmembers consist of three screw fittings, adjustment of any of whichaffects the spacing between the base member and the optical bench at thepoint of the fitting.

3. A lighting unit according to claim 2, wherein the said screw fixingsare arranged in a triangle having one side transverse of the lightingunit.

4. A lighting unit for use at an airfield runway or the like to providea pilot of a landing aircraft with visual information regarding a pathto be followed in making a safe landing, comprising an optical benchincluding at least one lamp, a screen with a horizontal slot and,between the lamp and the screen, a filter member divided horizontallyinto portions imparting two different colors to light transmittedtherethrough, whereby in operation a beam of light divided horizontallysubstantially about a medial plane into two constrasting portions isproduced,

a mounting member to which the lamp is fixed in preset location andorientation and means for releasably holding the mounting member in theoptical bench in invariant location and orientation with respect to thebench.

5. A lighting unit according to claim 4, wherein the said mountingmember is a fiat plate and wherein the optical bench includes aplurality of seating surfaces against which the plate is clamped.

6.A lighting unit according to claim 4, wherein the mounting member is aflat plate which fits in slots in the optical bench, clips beingprovided for holding the plate in place.

7. A lighting unit for use at an airfield runway or the like to providea pilot of a landing aircraft with visual information regarding a pathto be followed in making a safe landing, comprising a substantially flatbase member adapted to be anchored to and be held rigid by a fixedstructural support and a self-contained rigid optical bench comprising alamp, a screen with a horizontal slot and,

between the lamp and the screen, a filter member divided 20 horizontallyinto portions imparting two diiferent colors References Cited in thefile of this patent UNITED STATES PATENTS 1,765,354 Werner June 17, 19302,498,294 Pennow Feb. 21, 1950 2,559,415 Field July 3, 1951 FOREIGNPATENTS 830,043 Great Britain Mar. 9, 1960

7. A LIGHTING UNIT FOR USE AT AN AIRFIELD RUNWAY OR THE LIKE TO PROVIDEA PILOT OF A LANDING AIRCRAFT WITH VISUAL INFORMATION REGARDING A PATHTO BE FOLLOWED IN MAKING A SAFE LANDING, COMPRISING A SUBSTANTIALLY FLATBASE MEMBER ADAPTED TO BE ANCHORED TO AND BE HELD RIGID BY A FIXEDSTRUCTURAL SUPPORT AND A SELF-CONTAINED RIGID OPTICAL BENCH COMPRISING ALAMP, A SCREEN WITH A HORIZONTAL SLOT AND, BETWEEN THE LAMP AND THESCREEN, A FILTER MEMBER DIVIDED HORIZONTALLY INTO PORTIONS IMPARTING TWODIFFERENT COLORS TO LIGHT TRANSMITTED THERETHROUGH, WHEREBY IN OPERATIONA BEAM OF LIGHT DIVIDED HORIZONTALLY SUBSTANTIALLY ABOUT A MEDIAL PLANEINTO TWO CONTRASTING PORTIONS IS PRODUCED, ADJUSTING MEMBERS BY MEANS OFWHICH THE OPTICAL BENCH IS MOUNTED ON THE BASE MEMBER, THE ADJUSTINGMEMBERS ENABLING THE ORIENTATION OF THE OPTICAL BENCH RELATIVE TO THEBASE MEMBER TO BE ADJUSTED, A MOUNTING MEMBER TO WHICH THE LAMP IS FIXEDIN PRESET LOCATION AND ORIENTATION, AND MEANS FOR RELEASABLY HOLDING THEMOUNTING MEMBER IN THE OPTICAL BENCH IN INVARIANT LOCATION ANDORIENTATION WITH RESPECT TO THE BENCH.